Harping Midi is shareware, it means that it's a free to try software, but not freeware.

If you want to enjoy the advanced features or just because you really like it and want to support its development then you can subscribe and register your copy.

When you register the software online you will get a serial code. After entering this code along with your name and email address into Harping Midi (under the Help menu) it will get fully unlocked.